The present invention relates to an information providing apparatus and method, an information receiving apparatus and method, an information providing system, and a transmission medium and more particularly to an information providing apparatus and method, an information receiving apparatus and method, an information providing system, and a transmission medium enabled to transmit more messages without affecting video information, which essentially is to be transmitted by synthesizing EPG information from first information and second information.
Recently, digital television broadcasting was started in Japan, too, and programs have come to be offered to the audience on 100 or more channels. Such an increase in the number of programs complicates the operation to select a desired program out of them. Also, as the number of channels increases, on top of an increase in the quantity of the information involved, a program schedule for not only one day but also for a week or so ahead becomes required by the audience for watching programs in a planned manner. For this reason, the data quantity of the program schedule becomes tremendously large, and it becomes difficult for paper media, mainly newspapers, to provide program schedules as before. Moreover, in case there is a change in the broadcast schedule of any program, it is difficult to change the program schedule on a paper medium.
In this connection, it is proposed that an EPG (Electronic Program Guide) to support program selection should be transmitted from the program provider's side to the audience. As international standard on this EPG, the format of DVD_SI (Digital Video Broadcast Service Information) is prescribed.
If a program schedule is turned into data as EPG and offered to the audience, extraction of EPG data received by a receiving apparatus will enable the titles of programs, a program schedule, channel logos and the like to be indicated on the display, and the desired program to be quickly and correctly selected. Furthermore, any alteration in the broadcast time of a program can be easily coped with, and the viewer can correctly reserve the video recording of or watch the desired program.
FIG. 16 shows an example of a variety of tables constituting an EPG according to the prior art. An NIT (Network_Information_Table) states the overall configuration of the network and information necessary for reception, and one NIT exists for each network. In this NIT is stated an SDT (Service_Description_Table).
An SDT exists for each stream. For instance, if this EPG is to be transmitted via a satellite, an SDT is defined for each carrier wave (each transponder). In an SDT, information on the channel for transmission on the carrier wave is stated in pfEIT, gEIT and dEIT. In the pfEIT (present_following_Event_Information_Table) are stated the program currently broadcast on that channel and the next program. In the dEIT (detail-Event_Information_Table) is stated a document concerning an outline of the event (program), and in the gEIT (general-Event_Information_Table) is stated information other than the outline document concerning the program.
On the other hand, where NVOD (near video on demand) service is operated, a dummy channel (d-ch) is provided besides the channel on which program information is delivered (ch). In the dEIT and the gEIT of the dummy channel, the outline document and other information on the program broadcast by NVOD are respectively stated. On the other hand, in the dEIT and the gEIT of the channel on which the video information of NVOD is actually broadcast, the dEIT or the gEIT of the dummy channel is respectively stated and referred to.
Further, when transmitting messages from the originating side to the receiving side, the messages were inserted into the NIT.
However, transmission of messages by NIT involved the problem that the number of messages that could be transmitted was small because an NIT basically has no structure allowing the carriage of many data.
As a result, it was almost only the network manager who could transmit message; for instance, when a program provider having a channel is to transmit an announcement of a special program, a notice of a campaign, a guide on how to watch or listen to a program, or the like to the audience, it was transmitted as detailed information on a program.
However, if messages are transmitted in this way as detailed information on a program, the contents of the same messages are transmitted as EPG information on all the programs, and this is not only wasteful, but also the transmission capacity for essential program information is that much reduced. Accordingly there was the problem that, when a viewer wanted to know essential EPG information (such as the content of a program), unnecessary information was displayed against his or her wish, resulting in inconvenience of handling.
Moreover there was the problem that if, for instance, it became necessary to replace the operating software for the receiving apparatus by downloading, its notice, and the content and method of the change could not be transmitted to the audience as message.
Furthermore, there was the problem that, if messages were to be transmitted by NIT, the need to transmit an NIT increased that much, and the probability of the occurrence of a situation in which no NIT could be received would correspondingly increase. Since an NIT basically carries information which the viewer needs when selecting a channel, should no NIT become impossible to be received, he or she would become unable to choose none of the programs on any channel.